This invention relates to a method for manufacturing a drug, especially aspirin, acetaminophen, or the like, in small beads to be placed in a capsule and to the drug thus produced. In particular, the method involves preparation of a drug using a coating, such as an aqueous polymeric coating, on at least a portion of the beads, which results in sustained release when traveling through the digestive system.
Time release capsules containing a drug are made by either microencapsulation or by coating a seed, referred to as the Nupareil seed coating process. In both the encapsulation process and the Nupareil seed coating process, however, it is not feasible to obtain 650 mg of the active ingredient in bead form to be enclosed in a zero sized capsule. In a microencapsulation process, nearly 25% of the capsule is sugar, starch and moisture with the remainder being the active ingredient. Consequently, only 450-500 mg of active ingredient may be contained in a zero sized capsule. In the Nupareil seed coating process, seeds are relatively large, commonly 20-40 mesh and, thus, coated seeds do not permit more than 500-550 mg to be encapsulated in bead form in a zero sized capsule.
An additional process involves granulation, in which the drug used is combined with a starch and other materials, including an adhesive, and the material is then forced through a screen. This process, however, also limits the amount of drug that can be encapsulated to less than 550 mg.
In U.S. Pat. No. 3,524,910 to Holiday et al., granules of aspirin are encapsulated in a gelatin capsule. Additionally, the patent discloses sustained release of a portion of the active ingredient over an extended period of time by coating some of the granules with ethylcellulose in order to provide an analgesic effect of prolonged duration. However, the Holiday et al. delayed release aspirin compound capsule has disadvantages in that a zero sized capsule would not be sufficiently large in volume for holding the aspirin compound. Additionally, ingestion of the aspirin compound may produce undesired gastric irritation.
Accordingly, it is desirable to provide an improved method for manufacturing sustained release aspirin in a capsule.